Cross-linked polyvinylpyrrolidone (PVPP) is a homopolymer of N-vinylpyrrolidone with a cross-linked structure and belongs to synthetic polymer excipients. It is a white or off-white powder, odorless and tasteless, with a porous structure and good fluidity. It is insoluble in common solvents such as water and ethanol. Its core application is to serve as an efficient disintegrant in preparations, insoluble in water but capable of rapid swelling.

The characteristics of PVPP include high swelling property, high disintegration efficiency and strong stability. It is stable to acid-base and temperature changes, does not interact with drugs, and is compatible with most formulation processes (direct tablet pressing, wet granulation, etc.).

In the industry, PVPP is classified into Type A powder and Type B powder. What is the difference between these two types?

The “Type A powder” and “Type B powder” of cross-linked polyvinylpyretin (PVPP) are common names in the industry for PVPP products of different particle size specifications‌. The main differences between them lie in the particle size (particle size distribution) and the subtle variations in the resulting fluidity, application scenarios and disintegration characteristics‌.

I. Particle size (core difference)‌

Type B powder: usually refers to cross-linked polyvinylidene with a relatively large particle size ‌. It has better fluidity and coarser particles.

Type A powder: usually refers to cross-linked polyvinylidene with a smaller particle size ‌. Its particles are finer, its fluidity is relatively poor, but its specific surface area is larger.

II. Liquidity

Type B powder (coarse-grained)‌ : Due to the larger particle size, ‌ usually has better fluidity ‌. This is an advantage in the direct tablet pressing process, as good fluidity helps the material to fill the mold evenly, ensuring a small difference in tablet weight.

Type A powder (fine powder)‌ : The fine particles result in relatively poor fluidity ‌. In direct tabulation, it may be necessary to control the process parameters more carefully or use it in combination with other excipients with good fluidity.

III. Disintegration performance (minor differences)‌

Initial swelling rate: Due to its large specific surface area, the initial water absorption and swelling rate of A powder (fine powder) is usually faster ‌.

Overall disintegration time: The disintegration effect is more dependent on factors such as the total amount of PVPP, tablet hardness, and porosity. Fine powder may provide a more uniform disintegration network in a specific formula.

Disintegration mode: Fine powder may produce a more uniform and fine disintegration effect; The coarse powder may appear slightly “granular” when disintegrating.

IV. Main application scenarios ‌

1. Type B powder (coarse)‌

The preferred choice for wet granulation tablets is: During the wet granulation process, larger particles are more resilient to the mechanical stress of granulation, less likely to be overly crushed, and can better maintain their porous structure and rapid water absorption and swelling ability, thereby providing efficient disintegration in the final tablets. Due to its good fluidity, it can also be used for direct tablet pressing, especially when the fluidity of other ingredients in the formula is poor.‌

2. Type A powder (fine):

The preferred choice for direct tablet pressing is: fine particles are easier to mix evenly with other powders during the dry mixing process. Although its fluidity is slightly poor, by optimizing the formula and parameters of the tablet press, it can be well applied to the direct tablet pressing process. In cases where rapid disintegration or high swelling is required: a larger specific surface area may enable fine powder to absorb water and swell at a faster initial rate when in contact with water. Chewable tablets, oral tablets: Fine powder helps to achieve a more delicate texture.

V. Conclusion

Overall, the main difference between PVPP Type A and Type B powder lies in the customer’s requirements for particle size and dissolution speed. It still depends on the customer’s own formula. But there is no difference in quality between the two.